Prime Minister Abhisit Vejjajiva on Friday said the campaign for a pardon for Thaksin Shinawatra lowers the status of the royal institution.

King Bhumipol Adulyadej is highly revered in Thailand. He is able to grant royal pardons and reduce sentences but usually only after the felon has served time in jail.

Mr. Thaksin was ousted in a military coup in 2006. He has since been convicted of corruption charges, and fled the country to avoid prison. His supporters, known as Red Shirts, are seeking a million signatures on a petition asking for a pardon.

Despite being in exile, Mr. Thaksin is able to rally strong support - recently more than 20,000 Red Shirts demonstrated in Bangko.

Buranaj Samutharak, a spokesman for Prime Minister Abhsit's Democrat Party, says the government is deeply concerned about Mr. Thaksin's ability to interfere with Thai politics.

"What's more worrying actually is Thaksin's continuation to influence social disruption - which since April's incident - has adversely affected Thailand's reputation," he said. "And through his continued action in causing political unrest in Thailand I think it's definitely something the government cannot take lightly."

In April, Red Shirts rioted in Bangkok and also forced the cancellation of a gathering of Asian leaders in Thailand.

Despite the riots, politicians allied with Mr. Thaksin recently won two by-elections in Thailand's rural northeast, where he remains very popular.

Chris Baker, an author and commentator on Thai politics, says the by-elections show that Mr. Thaksin's populist economic policies still have strong support among the rural poor.

"The Thaksin name still has a lot of pull in the northeast and particularly in the lower northeast," said Baker. "We are in a situation now where the electorate is calling the tune and the electorate seems to be saying we are still going to vote for pro-Thaksin people."

But Mr. Thaksin faces a major court case, which begins this month. The court is to rule on whether more than $2 billion of his funds, frozen after the coup, were obtained through corruption while he was prime minister.

A verdict is expected in October. Some political analysts say if the court finds in Mr. Thaksin's favor he and his allies will be strengthened in the lead-up to general elections that many political analysts expect next year.